Non-pareil cores were spray-coated with a chlorpheniramine maleate (an alkylamine antihistamine) layer and a Eudragit(R) NE30D overcoat in a Wurster air-suspension apparatus. In vitro dissolution studies demonstrated that drug release was a function of polymer membrane thickness. Polyethylene glycol 6000, as a hydrophillic additive, increased the in vitro release of chlorpheniramine maleate from the pellets. Pellets coated with 8.30% Eudragit(R) NE30D, 0.50% talc and 1.00% polyethylene glycol 6000 were found to display desirable controlled release characteristics for chlorpheniramine maleate over the 8-h testing period, which were also comparable with that of Dykatuss(R) capsules. The controlled release pellets exhibited first-order release characteristics for chlorpheniramine maleate. Reproducibility of the manufacturing conditions employed in the study were confirmed thus ensuring reproducibility of drug release characteristics between batches of chlorpheniramine maleate pellets. Drug release from the pellets was shown to be independent of the dissolution method and medium used. Pellets displayed no significant change in drug release characteristics relative to the initial drug release data when stored for 12 weeks at room temperature (20 +/- 2 degrees C) and for 8 weeks at a low temperature (5 +/- 1 degrees C). However, pellets stored at 37 degrees C with 80% relative humidity and at 40 +/- 2 degrees C showed a slower in vitro drug release after 8-week storage and therefore failed to maintain their initial drug release profile.